DTrace is a dynamic tracing tool for analysing or debugging the whole system. Specifically, dtprobed is a component of the DTrace system that keeps track of USDT probes within running processes, parsing and storing the DOF they provide for later consumption by dtrace proper.
A vulnerability has been found in dtprobed that allows for arbitrary file creation through specially crafted USDT provider names.
The worst possible outcome is the ability for an attacker to run arbitrary code via the maliciously created file.
There is no known workaround at this time.
All DTrace users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=dev-debug/dtrace-2.0.6"